Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEMS AND METHODS FOR IMPROVED
NETWORK BASED CONTENT INSPECTION
FIELD OF INVENTION
The invention relates to network based content inspection (NBCI). More
specifically, the invention
provides systems and methods for improved NBCI in complex networks that are
typical for
enterprises and service providers. These networks are shared by large numbers
of concurrent users
who send and retrieve application content of various sizes via a variety of
communication
protocols. This invention improves the efficiency of the NBCI of an individual
communication
session by learning from the processing results of other communication
sessions which may be
carried via different network protocols without weakening. the overall
security of the network. In
addition, the invention provides methods to improve the stability of NBCI
systems by minimizing
the risk of system resource exhaustion if subjected to a burst of large
payloads. The invention also
improves perceived network stability by preventing the system resources from
being "live-locked"
by a few large content inspection tasks. Further still, the invention improves
the cost-effectiveness
of NBCI by allowing the optimization knowledge gained by one NBCI node be
shared with other
nodes.
BACKGROUND TO THE INVENTION
Network based content inspection (NBCI) is a technology that accumulates data
packets transmitted via
a data network, reconstructs the accumulated packets into payloads of
application level protocols,
inspects the reconstructed payloads, and invokes predefined actions according
to the result of the
inspection. Network based content inspection is increasingly becoming an
enabling method of
monitoring network data in a number of important applications such as cyber
surveillance, content
access control, network traffic monitoring, anti-virus, anti-spamming, content
annotation, content
caching, and other applications.
One problem of past methods of NBCI is reduced network performance as a result
of the time required
for content reconstruction, inspection, and manipulation. Generally, network
performance can become
severely compromised when there are many users accessing large volumes of
compressed content. As
the exchange of large archived content is common over today's data networks,
the inspection of such
content can be highly inefficient at certain times, for example, when there is
a new release of popular
software, digital images, videos, ring-tones, and other compressed content
that are being accessed by a
large number of users within a relatively short time-frame on a network.
It is also known that certain inspection tasks, such as 100% accurate
polymorphic virus scanning, are
NP-Complete problems. For these tasks, and with the increase of content size,
the computational
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resources required to complete such inspection tasks grow exponentially which
translates into long
network latency for NBCI systems, which in turn results in low network
throughput.
Performance is not the only issue. NBCI systems have a finite number of system
resources, thus, when
a system is subjected to communication sessions that carry large archived
payloads, system resource
exhaustion will happen. As a result, the system will either stop responding to
new communication
sessions, or will fail to open, which means that the very function of NBCI
will not be applied to the
new communication sessions. Therefore, past NBCI systems are generally not
stable for today's
enterprise and service provider networks.
A typical enterprise or service provider may deploy NBCI systems at many
network junctions. Past
approaches often duplicate the inspection of different instances of the same
content in each of the NBCI
systems. Therefore, on the whole network level, computing resources are wasted
on duplicated tasks.
In other scenarios, when many instances of the same content arrive at the same
time, past NBCI system
will spend system resources inspecting each of the instances. Such duplication
results in more resources
being required which drives up the cost of NBCI systems.
A review of the prior art indicates that several technology exist in the art
that enhance the performance
of NBCI systems.
For example, US 2006/0221658 (Gould) uses a programmable finite state machine
implemented as an
integrated circuit to improve the memory usage efficiency of applying pattern
matching against data
payload for the purpose of content inspection. However, as today's network
payloads typically contain
archived content and while pattern matching is a necessary step for several
NBCI applications,
significant amounts of CPU cycles and memory must still be spent on de-
archiving and re-archiving the
content. Moreover, this cost is encountered for the inspection of every
instance of the content on every
NBCI system.
US Patent 6,154,844 (Touboul) describes a method in which a Downloadable
Security Profile (DSP) is
attached to the content payload. In this system, an NBCI will not inspect the
payload if the payload can
be associated with a DSP. While this approach effectively reduces the
computation needed for
inspecting the same content in the NBCI systems along the path of the content
transmission, the method
of attaching a DSP to the payload will cause compatibility issues downstream
as the downstream
systems will have to understand this DSP. In addition, for small payloads,
such as those typical for
short message services (SMS), this method significantly increases the size of
the resulting payload. Still
further, for large, archived payloads, this method does not take advantage of
the fact that some
components of the payload may have already been inspected. In addition, this
method does not solve
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the system resource exhaustion issue caused by high concurrency of network
data traffic or the system
resource "live-lock" issue caused by inspection of large content.
With the rapid growth of network bandwidth, from 100Mbits, to 1 Gbits, and to
10Gbits and beyond,
the importance of NBCI performance is increasingly becoming paramount in the
effective management
of large, complex networks. As a result, there continues to be a need for NBCI
methods that effectively
and efficiently process data payloads in order to improve the efficiency,
stability while reducing NBCI
costs without compromising network speeds.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a method of enhancing
network based content
inspection for data payloads within heavy traffic data networks that are
typical for service providers
and enterprises by:
subjecting a data payload that may be carried via a variety of communication
protocols to a
content recognition module for determining if the payload or a component
thereof has been
previously inspected, or is being inspected; and
a) if the content has been previously inspected, associate this payload with a
previous inspection result for policy enforcement without inspecting this
payload;
b) if a previous instance of the content is being inspected, in order to
preserve the
NBCI system resources, the inspection of the instance will wait until the
inspection
of the being inspected instance is completed;
once inspection is completed, delivering the payload and inspection result.
In another embodiment, the method includes subjecting an unrecognized payload
to content
inspection to produce an inspection result and subsequently storing the
inspection result in a
content recognition module.
In another embodiment, for a given content inspection task, the NBCI system
resource allocation
priority is adjusted with the passage of time so that other communication
sessions can have a share
of system resources.
In yet another embodiment, the method allows several NBCI systems in a network
to learn from
each other's content inspection results.
In further embodiments, the method provides further functionality including
any operative
combination of various functions as described below.
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In one embodiment, the content recognition module includes a one-way hash
function for
calculating a message digest of the data payload and wherein the message
digest is compared to
previously stored message digests from previously inspected data payloads.
Message digests from
previously inspected data payloads are stored in a look-up table and the
content recognition module
returns a previously inspected result if the message digest of the data
payload is the same as a
previously stored message digest. As well, the content recognition module
returns a null result if
the message digest of the data payload does not correspond to a previously
stored message digest.
This payload is then subjected to content inspection and is further subjected
to a one-way hash
function to calculate a message digest of the unrecognized result and the
message digest
subsequently stored in the content inspection module.
In further embodiments, the knowledge of what content has been inspected or
what content is under
inspection is stored in a Content Inspection History Lookup (CIHL) table as a
record. Each record,
hereafter referred to as CIH record, in the CIHL table is indexed with a
unique signature of the
content. This signature is in the form of a message digest such as those
created with SHA- 1, MD-5,
etc. Each entry also contains a field to indicate if the content is currently
under inspection.
The CIHL table may also contain a field for the inspection result which may be
instructions to take
subsequent action with respect to the data payload. Additional information may
be added as fields
to a CIH record. In one embodiment, this additional information may be time of
inspection that
may be part of a system to enhance security such that a data payload is no
longer marked as
inspected if the time of creation information exceeds a pre-determined value.
Other information
may include size information.
In a further embodiment, the system and method enable many copies of data
payloads of the same
content entering a network via a variety of communication sessions and via
different
communication protocols to be effectively and efficiently inspected.
In a further embodiment, the system and methods associate a message digest
with supplementary
information such as time stamp, payload size, etc, to minimize the risk of
message digest collision-
based attacks against a NBCI system.
In another aspect of the invention, the payload is data of an application
level network protocol and
the payload may be decomposed prior to content inspection.
In another embodiment, the invention provides a system implemented on a
computer or a network
of computers for enhancing network based content inspection of a number of
concurrently received
data payloads comprising:
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a content recognition module for recognizing if each data payload has been
previously
inspected for content or is currently under inspection and a) allowing a
recognized data
payload to be delivered without content inspection; and b) subjecting an
unrecognized data
payload to content inspection to produce a content inspection result and
subsequently
storing the content inspection result in the content recognition module.
In another aspect of the invention, the inspections of multiple data payloads
are scheduled by a
content inspection scheduler that assigns and modifies the system resource
allocation priority to an
inspection task.
In various embodiments, the content inspection module is a co-processor and/or
the content
inspection module utilizes CAM (Content-Addressable Memory).
Further still, the system may include at least two content inspection modules
operatively connected
to a common look-up table, the results of content inspection on at least two
content inspection
modules is added to the common look-up table and/or the content recognition
look-up tables are
synchronized with each other.
BRIEF DESCRIPTION OF DRAWINGS
The invention is described with reference to the figures wherein:
Figure 1 is a schematic block diagram showing the interaction of a content
recognition
module and a content inspection module within a computer system, a co-
processor, or a
software module in accordance with one embodiment of the invention;
Figure 2 is a schematic block diagram of an implementation of the content
recognition
module;
Figure 3 is the structure of a content inspection history (CIH) record;
Figure 4 is a flow diagram of a method of processing a payload in accordance
with one
embodiment of the invention;
Figure 5 illustrates the state machine of the content inspection state
transition;
Figure 6 is a flow diagram of a method of processing a payload including
decomposition
of the payload and partial recognition of the payload where content inspection
is only
conducted for portions not previously inspected;
Figure 7 is a schematic block diagram of an implementation of the content
inspection
module;
Figures 8 and 8A are flow diagrams of a method of using a "Time Quantum
Divided"
strategy to apply content inspection algorithms to a payload in accordance
with one
embodiment of the invention;
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Figure 9 is a schematic block diagram of the implementation of the system of
the invention
using a content co-processor in accordance with one embodiment of the
invention; and,
Figure 10 is a schematic block diagram of a network showing how multiple
servers on a
network may learn from the content inspection performed by other servers.
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DETAILED DESCRIPTION
With reference to the Figures, systems and methods for optimizing the
computation required to
perform content inspection on concurrently received network data packet
payloads are described. In
the context of this description "concurrently" means data payloads received by
a computer network
within a short time period such that the system resources considers the data
payloads to have been
effectively received at the same time or within a short time period.
With reference to Figure 1, a content recognition module (CRM) 12 receives a
data payload 14.
The CRM 12 inspects the data payload to determine if the content of this
payload 14 has been
inspected previously or is currently under inspection. If the CRM 12
recognizes that the content of
the payload 14 has been previously inspected, the CRM will deliver the
recognized payload 14a
(together with an inspection result as explained below) without subjecting the
payload to content
inspection. If the CRM 12 determines the#ayload is an unrecognized payload
(that is, the payload
has not been inspected previously), the unrecognized payload 14b is delivered
to a content
inspection module (CIM) 16. The content inspection module 16 calculates the
inspection result and
delivers the inspected payload 14c together with the inspection result. If the
CRM recognizes that
the payload 14 is under inspection, the CRM will delay processing of other
payloads containing the
same content.
A policy module 15 will apply a set of operations, such as the downstream
delivery of the
recognized payload 14a, or modify the payload, based on business specific
policies. An inspected
payload 14c and inspection result 14d is returned to the CRM 12 in order that
subsequent receipt of
a similar payload does not pass through the content inspection module 16.
Generally, an inspection
result is one or more markers that indicate that the content has been
inspected and/or classified, and
that enable other functions to be performed on the payload according to pre-
determined policies.
With reference to Figures 2, 3, 4 and 5, the functionality of the CRM 12 is
described. Initially, the
payload 14 is passed through a one-way hash function to calculate a message
digest 20 of the
payload. The message digest is then passed through a Content Inspection
Scheduler (CIS) 22 that
compares the message digest 20 with previously stored message digests within a
Content
Inspection History Lookup (CIHL) Table 24. Each record 42 (Figure 3) within
the CIHL Table 24
is uniquely identified with a message digest. If a null matching record is
found, meaning that the
digest does not correspond to a previously stored digest, the payload content
14b is passed to the
content inspection module 16 for inspection by the content inspection module
16. The content is
then marked as "Under Inspection" 25 (Figure 4) by adding a CIH record 42c
into the CIHL table
24. This record will have its Inspection State 43 set to the value of "Under
inspection". The content
inspection module 16 scans the payload for content and classifies the content
based on pre-
determined criteria.
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After inspection, the newly inspected content 14c is passed through the one-
way hash-function to
calculate a message digest 20a of the newly inspected content 14c. A CIH
record 42b is inserted
into the CIHL Table 24. This entry has the message digest 20a, the Inspection
State "Inspected",
the Inspection Result 14d, and optionally other supplementary information as
will be explained in
greater detail below.
If the comparison returns a matching CIH record 42 with the Inspection State
field 43 being "Under
Inspection" (Step 29), meaning a previous payload carrying the same content is
currently being
inspected, the processing of the latter payload content will wait for a period
of time 26 before
continuing. When the system determines that the inspection state of the
previous payload content
(Figure 4, step 27) has changed to "inspected", the latter payload content
will be subjected to
content recognition.
If the comparison (step 28) returns a matching CIH record 42 with the
Inspection State field 43
being "Inspected", meaning that the digest corresponds to the message digest
of previously
inspected content, the payload by-passes the content inspection module 16 as
recognized payload
14a.
The one-way hash function may be a known Secure Hash Algorithm (SHA), such as
SHA-1, MD2,
MD4, MD5, variations thereof or other hashing algorithms as known to those
skilled in the art.
With reference to Figure 6, an altemate embodiment is described that further
enhances the
efficiency of content inspection. In this embodiment, a methodology allowing
partial recognition of
the payload content is conducted in order that content inspection is only
needed for the portion of
the payload content that has not been previously inspected.
In this embodiment, the payload is decomposed into logical portions 30 and
each portion is
evaluated to determine if it has been inspected. If the algorithm determines
that there are un-
inspected portions (step 31), a message digest (step 32) is calculated for the
un-inspected portions.
Each message digest is then searched within the CIHL table as described above.
Decomposition may be achieved by breaking down a payload into logical portions
such as by
attachment within an email, or the file content within a zip file.
Scheduling Manager
In a preferred embodiment, scheduling the content inspection of multiple
inspection tasks is
conducted to prevent system resource exhaustion in the event of the rapid or
simultaneous arrival of
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many different data payloads, many instances of the same content, or in the
event of a deny-of-
service attack. Scheduling will ensure that the system resources are
efficiently utilized to complete
content inspection and are spent on applying the content inspection algorithms
to one only instance
of any multiple instances. This is achieved by giving much lower priority to
time-consuming or
system resource demanding content processing tasks. Scheduling is accomplished
by utilizing the
content inspection state (ie un-inspected, under-inspection or inspected)
together with information
relating to the number of required inspection tasks, the time of receipt of an
inspection task and the
size of the inspection task.
Figures 7, 8 and 8A describe one embodiment of the Content Inspection Module
(CIM) 16a using a
"Time Quantum Divided" (TQD) content inspection process scheduling strategy.
This process
enables the system to enhance speed of service to multiple users accessing a
network by decreasing
priority for a content inspection process with the passage of time. For
example, in a situation where
there are 100 users accessing a network, and 99 of those users are attempting
to pass small payloads
(eg. a 1-2 kb file) through the network and I user is attempting to pass a
larger file (eg. a 100 Mb
file) through the network, the scheduling manager will assign priority and
allocate system resources
based on both the size of each inspection task and the time taken to complete
each content
inspection task in order to minimize or prevent system resources being
consumed by the single,
larger inspection task, thus preventing each of the multiple users passing
smaller payloads having
to wait for the completion of the single larger inspection. That is, the
system is able to prevent
"live-lock" of the system resources by lengthy content inspection tasks.
As shown in Figures 8 and 8A, a content inspection process 80 starts by
registering each content
inspection task with the TQD CIP manager (Figure 8, step 82) as each content
packet requiring
inspection arrives thus defining "n" inspection tasks. Upon registration, the
TQD CIP manager 90
(Figure 8A) periodically adjusts priority for each content inspection task
such that each content
inspection task is completed in a manner to maintain quality of service to
multiple users by
balancing the time to complete an inspection as determined by the number of
inspection tasks, and
the relative size of each inspection task. Once the inspection algorithms have
been completed (step
84) based on the TQD CIP manager 90 assigned priority, the CIHL table is
updated (step 86) with
the inspection result and the content inspection process 80 un-registers a
specific content inspect
task from the TQD CIP manager (step 88).
As content inspection tasks are being registered and un-registered from the
TQD CIP manager 90,
the TQD CIP manager 90 continuously loops through each of the registered
content inspection
tasks and reviews and updates the status or priority of each content
inspection task.
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With reference to Figure 8A, initially, the TQD CIP manager 90 determines if
there are any
registered inspection tasks (step 92). If there are no registered inspection
tasks, the TQD manager
90 waits a pre-determined period of time (step 94) until re-determining if
there are any inspection
tasks. If there are inspection tasks (step 93), the TQD CIP manager 90 will
reduce the time-to-live
(TTL) value of each inspection task by a certain value (step 98). A content
inspection process
(CIP) will be aborted (step 102) if its TTL drops below an arbitrary threshold
value (step 100). The
CIH record of an aborted inspection task will be removed from the CIHL table
(step 104). The
transmission of the payload may be re-initiated by the sender and/or receiver
at a later time.
If the TTL is not less than zero, the TQD CIP manager 90 will reduce the
priority for the ith
inspection task (step 106) by a pre-determined value.
Once the priority has been adjusted or the ith CIP has been aborted, the TQD
CIP manager
determines if there are any remaining registered inspection and either waits
for a period of time
(step 94) to check for registered inspection tasks or continues reviewing and
adjusting the status of
other registered inspection tasks.
As an example of a possible scheduling scenario, 5 content inspection tasks
may have been
registered with the TQD CIP manager 90. These registered inspection tasks may
include 3 small
files (eg. 3 kb each), 1 medium size file (eg. 10 Mb) and I large file (eg.
100 Mb) received in any
particular order. In processing these inspection tasks, the manager will seek
to balance the content
inspection in order to maintain efficiency for a desired level of service. For
example, scheduling
manager parameters may be set to ensure that priority is assigned to
inspection of the smaller files
first irregardless of the time of receipt. Alternatively, scheduling manager
parameters may be set to
ensure that priority is assigned strictly based on the time of arrival
irregardless of size. As
illustrated in Figure 8A, the system may assign the same initial priority to
all the inspection tasks.
The scheduling manager then reduces the priority for each of the task with the
passage of the time.
Further still, scheduling manager parameters may be set as balance between
time of arrival and
size. That is, in certain situations, the large file may be processed
concurrently with the smaller
files based on a particular allocation of system resources. Alternatively, the
large file may be
processed only for a period of time, until the scheduling manager determines
that processing has
taken too long and the inspection process is aborted for the large file. It is
understood that the
number of tasks registered with the scheduling manager may be dynamically
changed such that
priority may be adjusted up or down based on changes to the number of
registered tasks.
It is understood by those skilled in the art that the determination of
priority and the allocation of
system resources to effectively manage content inspection based on content
size, and time-to-
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complete an inspection task may be accomplished by a variety of algorithms and
that the
methodologies described above are only a limited number of examples of such
algorithms.
Classification of Inspection Resuks
In various embodiments, the content of a data payload, as a recognized payload
14a or an inspected
payload 14c can be associated with further information as described below
allowing the system to
take particular actions with respect to the payload based on the inspection
result (Figure 3).
a) Classification of Content
The inspection result can be classified on the basis of content. For example,
it can be a marker
indicating that the content is spam, spyware or a virus.
b) Content Instructions
The inspection result can include a set of instructions to alter the content.
In this case, the policy
module 15 may use these instructions to take further steps with respect to the
payload. For example,
if the content is marked as a virus, the instructions may be to warn the
recipient that the payload
contains a virus and should not be opened. In other examples, the instructions
may be to prevent the
delivery of payload, but to send information indicating that the delivery has
been denied.
c) Supplementary Data
The inspection result can be associated with supplementary data. Supplementary
data provides
further functionality including enhanced security to the methods of the
invention.
For example, supplementary data may include the time of creation 44 of the
message digest which
may be used to provide enhanced security. That is, as it is known that given
enough time, an
attacker can achieve a collision with the commonly used one-way hash
algorithms, by adding time
information as supplementary data, a message digest can be retired if the
message digest is older
than a pre-determined value.
In another embodiment supplementary data may also or alternatively include the
size 45 of the
payload wherein the size information can be used to provide finer granularity
to also reduce the
possibility of a hash code collision. In this example, when conducting the
CIHL table search
function within the lookup table, both the message digest and the size have to
match those of the
payload.
Deployment
The system may be deployed as an adaptive external module of an existing
content inspection
system, or as an embedded module within a content inspection system.
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In one embodiment, the system is implemented with the content recognition
module interacting
with an existing content inspection co-processor as shown in Figure 9.
In another embodiment, the system is a software component embedded into a
content inspection
module which is a software module, a co-processor or a computer system.
In a further embodiment, and in order to leverage the computation spent on
content inspection, the
message digests along with the inspection results can be shared among several
instances of content
recognition/inspection systems as shown in Figure 10. The sharing can be
accomplished by storing
the message digests along with the inspection results in a central server
shared by these instances of
content recognition/inspection systems, or replicating the digests along with
the inspection results
in each instances of the group. For example, Figure 10 shows four networked
servers that each have
external Internet connections that are securely linked via a common internal
network. Server 3 is
shown to represent the highest traffic server, possibly as an enterprise
gateway. Servers 1, 2 and 4
see less traffic but are operatively and securely connected to Server 3. A
NBCI database is
connected to Server 3. In order to further enhance the efficiency of the
system, each server may
report the results of their respective payload inspections to Server 3 and
hence to database 5 such
that each server on the system can "learn" from the experiences of the other
Servers, thereby
preventing the duplication of content inspection across a larger network. This
networked
embodiment is particularly beneficial in larger enterprises or service
providers where the volume of
traffic is sufficiently large that the ability to share such inspection
results can greatly enhance the
overall efficiency and cost-effectiveness of the system.
The preceding description is intended to provide an illustrative description
of the invention. It is
understood that variations in the examples of deployment of the invention may
be realized without
departing from the spirit of the invention.
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